Proposed rule · 2026-00021

National Primary Drinking Water Regulation for Perchlorate

The U.S. Environmental Protection Agency ("EPA" or the "Agency") is proposing a National Primary Drinking Water Regulation (NPDWR) for perchlorate and a health-based Maximum Contaminant Level Goal (MCLG) under the Safe Drinking Water Act (SDWA). In this action, the EPA is proposing to set the perchlorate MCLG at 0.02 mg/L (20 [micro]g/L). The EPA is also proposing and taking comment on setting an enforceable Maximum Contaminant Level (MCL) for perchlorate at 0.02 mg/ L (20 [micro]g/L), 0.04 mg/L (40 [micro]g/L), or 0.08 mg/L (80 [micro]g/L). The EPA is also proposing requirements for water systems to conduct monitoring for perchlorate in drinking water, take mitigation actions if the level exceeds the MCL, provide information about perchlorate to their consumers through public notification and consumer confidence reports, and report to their respective primacy agency. The Administrator has determined that the benefits of this regulation would not justify the costs; however, the EPA is required to issue an NPDWR and MCLG for perchlorate in response to the D.C. Circuit's decision in NRDC v. Regan.